Biomedical Engineering Reference
In-Depth Information
Figure 4.
The SEM micrographs of tensile fractured surfaces of 40 (left) and 20 mass% (right)
reinforced multilayer web reinforced composites.
Ibrahim et al. (2010) investigated similar trends. They investigated compression
molded kenaf fiber reinforced PLA with fiber loads ranging between 10 and 50 mass%.
The tensile strength decreased from 27 N/mm² measured for the 20% kenaf PLA com-
posites to 16 N/mm² measured for the 40% kenaf PLA composites. And Oksman et
al. (2003) described similar effects for compression molded flax-PLA. The tensile
strength of 40% flax-PLA decreased compared to 20% flax-PLA. They partially at-
tribute this behavior to poor adhesion between fiber and matrix.
A more detailed presentation of the influence of the semi-finished product on the
mechanical composite characteristics is given in Graupner and Müssig (2009).
Lignin Treatment
An improvement of the tensile characteristics of the multilayer web reinforced com-
posites produced by compression molding technique CP-1 was reached by the treat-
ment of the multilayer webs with lignin. While the pure PLA sample and the lignin
treated PLA sample showed no clear differences between tensile strength, Young´s
modulus and Charpy impact strength (Table 1) clear influences of the lignin treat-
ment were determined for the composites. This supports that the lignin interacts just
between fiber and matrix or improves the compatibility of the molded composites and
has no influence on the mechanical characteristics of the pure PLA matrix.
Mechanical investigations of 40 mass% lignin treated multilayer web reinforced
PLA composites have shown improved tensile strength and Young's modulus values
in comparison to the untreated composites. Considering the tensile strength the values
increased from 28 to 57 N/mm² for the lyocell 15.0-PLA composites, from 36 to 53
N/mm² for the lyocell 6.7-PLA composites and from 42 to 52 N/mm² for the lyocell
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